1. Field of the Invention
The present invention relates generally to an electrographic apparatus and more specifically to an improved structural arrangement in electrograhpic apparatus of the type having a flexible electrostatic image-bearing web or an intermediate flexible web, which arrangement achieves improved image transfer to paper by providing a zero tension loop in the web located after a transfer station and before detacking of the paper from the web.
2. Description of the Prior Art
It is known in the copying art to form buckles in a flexible electrostatic image-bearing web in its movement through the copier at various locations and for various functions. For example, U.S. Pat. No. 3,601,392, discloses the idea of interrupting the forward movement of a copy sheet with registration fingers and to form a buckle in the copy sheet by its continued feeding by upstream feed rollers to provide registration of the lead edge of the copy sheet before the copy sheet is fed into the image transfer station. U.S. Pat. No. 4,017,065, discloses a speed mismatch compensation system which allows the fusing roll nip to be closely spaced from the transfer station of an electrostatographic copier by a distance less than the movement dimension of an individual copy sheet. The intermediate portion of the copy sheet is selectively supported and guided in a manner so as to form a buckle which accommodates a speed differential between the fuser roll nip velocity and the velocity of the photoreceptor. Another example is U.S. Pat. No. 4,928,141, which discloses a copier wherein a copy sheet is longer than the distance between the transfer station and the fusing station. Thus the copy sheet forms a buckle therebetween. A sensor detects when the buckle reaches predetermined configurations and sends a signal to a stepping motor to increase or decrease the speed of the fuser to maintain the buckle configuration within the preassigned parameters. U.S. Pat. No. 4,013,041 discloses an electrographic apparatus employing a brush-type developer applicator which contacts one side of a flexible electrostatic image-bearing web, where the web is free to buckle in response to the varying contours of the applicator.
The ideal goal in xerography is to have high transference efficiency when the toner image is transferred to a sheet; machines that can achieve this for less cost will have a tremendous competitive edge. Thus far, the use of an electrically biased transfer roller, BTR for short, is a leader in achieving higher transfer efficiency. However, the BTR is relatively more expensive. The less expensive system, with better wearing longevity characteristics is the corona generating device. However, there is relatively less transfer efficiency with the corona than the BTR. Herein lies the problem, more expense for better efficiency or less expense for less efficiency.
Therefore, in response to this tradeoff of expense for quality, a need exists for a way to increase transfer efficiency while maintaining reduced costs.
As a result, the present invention provides a solution to the described problems and other problems, and also offers other advantages over the prior art.